Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 42 5 2004 10 15 383 389 N. Khadem Sh. Jalali Mazlouman 2015 09 28 It seems that endometriosis plays an important role in female factor infertility but a clear causal relationship has yet to be established. This case-control study was conducted to determine and compare the frequency and severity of endometriosis in 100 infertile women and 120 fertile multi-para women as control group. Descriptive statistics, Student t test and Chi square test were used in analyzing data. Endometriosis was diagnosed in 38% of infertile versus 11.6% in fertile women (P=0.002). The mean age of women with endometriosis was 27.9±6.1 years; maximum prevalence of endometriosis was observed at 26 years of age. The mean duration of infertility was 4.3±1.9 years in women with endometriosis and 4.6±1.2 years in women without endometriosis. The prevalence of endometriosis in study population was comparatively higher than what has been reported in studies from other countries. There was a significant relation between endometriosis and infertility. Diagnostic time interval had no relation with infertility and severity of endometriosis. Age-related factors did not have any effect on fertility in women with endometriosis. Our study demonstrates a meaningful relation between endometriosis and infertility. Endometriosis may have a higher prevalence in Iranian population. https://acta.tums.ac.ir/index.php/acta/article/view/2757 https://acta.tums.ac.ir/index.php/acta/article/download/2757/2739